testing for kernel features via the feature_present(3) libcall
The semantics are similar to the other macros in the header (skip
testcase with ATF macro; exit with appropriate exit code with the
PLAIN macro)
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
no longer bombs out
PLAIN_REQUIRE_KERNEL_MODULE: use printf + _exit, no err so the testcase no
longer bombs out if it prints to stderr
MFC after: 5 days
